It will make things easier for the transaction log backups for each database to be in its own backup device.

You can still restore items from the mixed backup device, just...

A transaction log backup does not cause the database transaction logs to be 'cleared'.  In the above scenario, a transaction log backup performed after the full backup will still contain transactions...

SQL Server has 3 recovery models - simple, bulk-logged and full.  Depending on your data recovery needs, you need to choose the recovery model that is most suitable for you. ...